Method of and means for regulating the transmission over electric circuits



' March 6, 1928.

H. NYQUIST Zuiumm' J I METHOD OF AND MEANS FOR REGULATING THE TRANSMISSION-OVER ELECTRIC CIRCUITS Original Filed Feb. 19, 1923 2 Sheets-Sheet l INVENTOR ATTORNEY March 6, 1928.

H. NYQUIST METHOD OF AND MEANS FOR REGULATING THE TRANSMISSION OVER ELECTRIC CIRCUITS Original Filed Feb. 19, 1925 2 Sheets-Sheet 2 Wwmzlszn'aw Wires INVENTOR Iggy/16M Z244 ATTORNEY Patented Mar. 6, 1928.

UNITED STATES PATENT OFFICE.

HARRY NYQUIST, OF JACKSON HEIGHTS, NEW YORK, ASSIGNOR TO AMERICAN TELE- PHONE AND TELEGRAPH COMPANY, A CORPORATION OF NEW YORK.

METHOD or AND MEANS FOR'REGULATING THE TRANSMISSION ovnn ELECTRIC omourrs;

Original application filed February 19, 1923, Serial No. 620,094. Divided and this application filed October 2, 1924. Serial No. 741,256.

This invention relates to electric transmission circuits and more particularly to long repeatered electric transmission circuits.

The object of the invention is to provide suitable methods of and means for maintaining substantially constant the transmission equivalent of electric circuits in spite of the effect upon such circuits of variations in humidity.

This application is a division of my copeuding application, Serial No. 620,094, filed February 19, 1923 and entitled Methods of and means for regulating the transmission over electric circuits.

it is well understood by those skilled in the art that varying humidity conditions cause variations of the leakage between the conductors of these transmission circuits. For the purpose of compensating for the effects of the humidity variations applicant provides an auxiliary circuit including one or more members whose conductivity increases or decreases with an increase or a decrease. respectively, of the humidity, an indicating device responsive to such changes in the conductance of the auxiliary circuit, and means for automatically regulating the gain of the repeaters in the transmission circuits in accordance with the indications of the above mentioned device.

It is proposed to show three desirable a1 rangemcnts embodying applieants invention, by way of specific illustration. lin each arrangement, the member upon which the humidity acts directly is placed so as to provide, in combination with the other elements of the arrangement, the desired comvpensation for the efiects of the varying, humidity conditions. Thereafter, there will be shown by way of illustration two desirable constructions of the peculiar member.

United States Patent No. 1,438,219, granted to Alva B. Clark, covers methods of and means for taking care of the effects of ten'iperature variations on the transmission circuits. One desirable embodiment of applicants invention is a modification of the system described in the above numbered patent, whereby the gain of the repeaters may be varied to compensate for the eifects of humidity variationswithout seriously affecting the ability of the system to take care of the temperature variations. Briefly, 5 Clarks means for taking care of temperature variation are disclosedas consisting essentially of a balance bridge, of which a pilot, wire in the cable forms one arm. a battery connected across said bridge, a galvanometer so connected as to give the desired indications. and means for varying the gain of the repeaters in the transmission circuits. An increase or a decrease in the resistance of the pilot wire. caused by a change of temperature results in the unbalancing of the bridge, which unbalancing operates through the means indicated above and briefly described below to vary the gain of the repeaters in the transmission circuits. thereby compen- 7 sating for the cited; upon the given circuit of the change in temperature. Applicant introduces an additional member in one arm of the balance bridge, as fully disclosed below, this member being so constructed and so placed as to provide compensation for the changes in humidity, thus serving to maintain substantially contant the transmission equivalent of the transmission circuits in spite of the humidity variation.

A second desirable arrangement of applicants system. based upon the same general principle as the first and including. like the first, a pilot wire, a balance bridge, and means for regulating the repeaters uponthe 8E5 unbalancing of the bridge, has the added advantage of providing compensation for the humidity variations at different. points in the circuits. which end is attained by the introduction at each ofiice of an auxiliary network connected in series with the pilot wire and including a member directly responsive to humidty changes.

In a third desirable arrangement, which is a modification of the second, a directly responsive member is connected across the two line wires of the auxiliary circuit at each ofiice. A

Applicants invention will be more clearly understood when the following detailed de- 10o scription is read in connection with the accompanying drawing. Figure 1 of the drawing shows schematically the essential features of the first desirable arrangement,

while Figs. 2 and 3 show in like manner the second and third desirable arrangements respectively. Fig. 1 shows a plan view and Fig. 5 a side elevation of one desirable con struction of the peculiar member referred to above, while Figs. 6 and 7 show similar views, respectively, of a second desirable construction of the same member. Like numeralsot reference in Figs. 1, 2 and 3 designate corresponding parts.

With particular reference to Fig. l. the pilot wire 1 forms one arm of a balance bridge, 2 is the battery connected across the bridge, andB is the galvanometcr. An arm of the bridge adjacent to the above mentioned arm comprises two parts in parallel, one part being simply a resistance 1, the other consisting of a resistance 5 and a member 12. This member 12 is so constructed that its conductivity increases with the increase in humidity to approximately the same degree as the conductivity of the cabling affected by such humidity increase. Two desirable constructions of this member are described in detail below. As the humidity increases and, consequently, the conductance ot' the member 12 increases-the balance bridge is unbalanced in the same direction as it would be it the resistance of the pilot wire 1 were increased. lln balancing, the bridge will increase the gain of therepcaters through well lmown mechanical means, as specificallydescribed in. the above numbered Clark patent. Briefly, this operation and the apparatus involved therein are described as follows: 19 indicates an adjustable resistance correspondin to resistance R of the above numbered lark patent, this resistance being automatically adjusted in the manner indicated in the said Clark patent, that is, when the galvanometer is deflected, the resistance is adjusted in accordance with the deflection oil the galvanometer by mechanical means so as to balance the bridge. As indicated in the above numbered Clark patent, the mechanical movement utilized to balance the bridge is also utilized to produce a corresponding change in thesetting of the potentiometers 20 and 21 (corresponding to P and P of the above numbered Clark patent) the setting of these potentiometers controlling the amplification of amplifiers 22 and 23 of the transmission circuits, respecttively, these amplifiers (which correspond to amplifiers A and A of the above numbered Clark patent) being shown symbolically. Thus there is efiected a suitable change in the gain of the repeaters of the transmission circuits. 7 1

With particular reference to Fig. 2, there is represented, as in Fig. '1, a pilot wire 1, forming one arm of the balance bridge, a battery 2, and a galvanometer 3. Three oilices, representative of any number of 0thces, are indicated as 6', 7 and 8, these ofiices -work including two parts in parallel.

being subject to 'dili'erent humidity conditions. At each otlice there is introduced in series with the pilot wire 1 an auxiliary net- The one part is simply a series resistance 9. The other part is made up of a battery 10,- a resistance 11, and a member 12 similar to the member 12 described generally in connection with Fig. 1. This network operates as follows: (1) in dry weather, practically no cur rent passes through the member 12, and consequently only the series resistance 9 is effective. (2} As the humidity increases, the member 12 becomes conductive, and as a result current flows through the shunt elementof the network. lln the absence of the battery 10 this would have the same effect on the bridge that a decrease in the resistance of the pilot wire would have. This change in the balance oil the bridge would be roughly proportional to the decrease in transmission of the circuits all'ected by the increase in humidity. Since the mechanism controlled by the bridge is designed primarily to in,- crease the gain as the resistance increases with the temperature, and vice versa, the change mentioned above would. be in such a direction as to decrease the gain of the repeaters. lit is therefore necessary to provide some means for translating the unbalancing efitect of the network into an efiective'unbalance in a direction opposite to that indicated alcove. For this purpose the batteries 10 are included in the shunt elements of the networks. The poling of the batteries 10 is to be noted. As indicated in the drawing,these batteries are poled in such a manner as to tend to cause a flow of current in the pilot wire in a direction opposite to that caused by the battery connected across the bridge. This produces an eifect equivalent to an increase or resistance in the pilot wire. The result is the same as that mentioned in connection with Fig. 1, viz, an increase in the gain of the repeaters.

With particular reference to Fig.v 3, at each of two oilices, representative of any number-0t otlices, there are connected across the two line wires of the auxiliary circuit a member 12 similar to the member 12 de' scribed enerally in connection with Fig. 1, and a hattery 1.0. As the humidity increases, the member 12 becomes conductive, and a current is caused toi'gflow in the line wires-with the results described above.

Figs. 4 and .5 show diagrammatically one desirable construction of the member labelled 12 in Figs. 1, 2 and 3. Two metal plates 13 and 14 form the terminals of the member. Between these two lates there i'splaced a layer of cotton 15, into which ma be introduced hygroscopic saltsf- Th plate 13 is perforated, as at 16. As is well known,

cotton is hygroscopic and-becomes 'conduc' tive when exposed to air of considerable ill till

humidity, By the introduction of hygroscopic salts, the effect of a change of humidity on the conductance of the member 12 can he further regulated and broughtto the exact point desired in connection with any given circuit.-

Figs. 6 and *4 represent a second desirable construction of the member 12 of Figs. 1, 2 and 3. A metal plate 17 correspomls to the plate 14- of Fig. 5 and constitutes one terminal of the member. Forming the other terminal is a layer of wire gauze 18. The layer between the plate I? and this upper layer of wire gauze is as described in connection with Figs. 4t and 5.

What is claimed is;

1. lln a system comprising a plurality of electric circuits subject to similar atmospheric conditions and a balance bridge associated with one of said circuits, the method of compensating for the eiieet of humidity variation on the transmission equivalent equivalentof the circuits. which consists incausing the humidity variation to unbalance the balance bridge associated with the one circuit, and causing the rebalancing of the bridge to produce compcnsatin change; in the amplification of the amplifying means in the other circuits.

3. lln a signalling system, a plurality of transmission circuits, a pilot wire subject to influences similar to those atl ect-ing the transmission cfliciency of said tiansmission circuits, a balance bridge, said pilot wire being included in one arm of saidbalance bridge, means associated with said balance bridge and adapted to change the current flow therein in response to humidity variation, a switch, means for automatically setting said switch in accordance with the current fiow in the balance bridge. and means controlled in accordance with the setting of said switch for adjusting the transmission efficiency of said transmission circuits.

4. As means for compensating for the effect of humidity variations on the transmission equivalent of repeater-ed circuits, an auxiliary circuit including an element whose conductivity varies with humidity change, a currentindicating device responsive to changes in the electrical characteristics of said auxiliary circuit, and a device designed to vary the gain of the repeaters in response to the current 111, and in accordance with the indications of, said current indicating device.

5. As means for compensating for the ctlect of humidity variations on the transmission equivalent of repeatered transmission circuits, a pilot wire, balance bridge including said pilot wire as one of its arms, a member whose conductivity varies with humidity, said member being included in an arm of the balance bridge adjacent to the arm which includes the pilot wire, a current indicating device responsive to changes in the electrical characteristics of the bridge,

and a device designed to vary the gain of the repeaters in response to current 111, and in accordance with the indications of, said current indicating device,

6. As means "for compensating tor the cflect of humidity variations on the transmission equivalent or" repeatered circuits, an auxiliary circuit including a. member comprising two conductive terminals, one of said terminals being perforated and an intermediate layer of material whose conductivity varies in proportion to the variation of humidity; a current indicating device rcsponsive to changes in the electrical characteristics of said auxiliary circuit; and a device. designed to vary the gain of the repeaters in response to current in, and in accordance with the indications of, said current indicating device.

. 7. As means for compensating for the effort of humidity variations on the transmissions equivalent repeatered transmission circuits, a pilot wire; a balance bridge including said pilot wire as one of its arms; a member comprising two conductive terminals, one of said terminals being perforated, and an intermediate layer of material whose conductivity varies in proportion to the variations of humidity, said member being included in an arm of the balance bridge adjacent to the arm which includes the pilot wire; a-current indicating device responsive to changes in the'electrical characteristics of the bridge; and a device designed to vary the gain of the repeaters in response to current in, and in accordance with the indica tions of, said current indicating device.

8, In a signaling system in which the transmission equivalent of repeatered trans mission circuits is maintained substantially constant in spite of changes in the resistance of such circuits, due to atmospheric changes, by causing the changes of resistance in a pilot wire to unbalance a balance bridge including said pilot wire as one of its arms, said bridge, in balancing, operating by mechanical means to vary the gain of the repeaters in the transmission circuits; a means for compensating for variations in leakage between the conductors, due to lllll lit humidity changes, said means consisting of a member whose conductivity varies with humidity, said member being included in an arm of the balance bridge adjacent to the arm which in"ludes the pilot wire.

9. In a signaling system in which the transmission equivalent of repeatered t'ansmission circuits is maintained substantially constant in-spite of changes in the resistance of such circuits, due to atmospheric changes, by causing the changes of resistance in a pilot wire to unbalance a balance bridge including said pilot wire as one of its arms,- said bridge, in balancing, operating by merhanical means to vary the gain of the repeaters in the transmission circuits; a

means for compensating for variations inleakage between the conductors, due to humidity changes. said means consisting of a member included in an arm of the balance bridge adjacent to the arm which includes the pilot Wire, said member comprising two conductive terminals, one of said terminals being perforated, and an intermediate layer of material whose conductivity varies in proportion to the variation of humidity.

10. I n a signaling system, a plurality of transmission efliciency of said transmission circuits, responsive means associated with menacesaid pilot circuit and adapted to undergo changes in electrical characteristics in response to humidity variation, translating means associated with said pilot circuit, said translating means being responsive to changes in the electrical characteristics of said responsive means and of said pilot circuit, and means for varying the electrical characteristics of said transmission circuits under the control of said translating means.

1:2. In a signaling system, a plurality of transmission circuits, a pilot circuit subject to influences similar to those affecting the transmission efficiency of said transmissioncircuits, responsive means associated with said pilot circuit and adapted to undergo changes in electrical condition in response to humidity variation, a switch, means for automatically setting said switch in accordance with the electrical conditions of said responsive means and of said pilot circuit,

and means controlled by .said switch for adjusting the transmission efl'iciency of said transmission circuits.

13. In a signaling systen1,'a plurality of tranmission circuits, amplifying means in said circuits, a 'pilot circuit subject to influences similar to those aifecting the transmission efliciency' of said transmission circuits, responsive means associated With-said pilot circuit and adapted to undergo changes in electrical condition-in response to humidit-y variation, a switch, means for automatically setting said switch in accordance with the electrical conditions of said responsive means and of said pilot circuit,

and means controlled by the setting of said i switch for adjusting the amplification of said amplifying means.

In testimony whereof, I have signed my name to this-specification this 30th day of September, 1924.

HARRY NYQ IS'L. 

